There are many industrial applications that benefit for having an object held securely in place, primarily manufacturing processes. In the past, a worker manually held the object in place with one hand and operated on the object with the remaining hand. This led to great manufacturing inefficiencies and safety concerns.
Clamps may be used to hold objects securely in place. However, the extra time and effort in placing and securing the clamps is also inefficient in a manufacturing process. Further, many objects have inconvenient shape or outlines that make efficient clamping difficult, if not impossible.
Recently, there has been increased interest in devices that use vacuum to hold or secure objects. These devices appear to fall into two categories: devices designed for assembly line type operations and devices designed for use with cargo moving vehicles. These all have the same limitations, i.e., they require a standing vacuum as a part of the system.
An example is U.S. Pat. No. 3,219,380 issued to Carliss ("Carliss"). The device disclosed in Carliss uses compressed air to create a vacuum that is stored in a vacuum tank. The vacuum tank is in open communication with vacuum valves that are located directly over the vacuum pads. When a sensor detects an object, the vacuum valve is opened to the vacuum pads, thereby evacuating the volume within the vacuum pad and securing the detected object to the vacuum pad.
Other examples are U.S. Pat. No. 3,314,559 issued to Horton ("Horton"). Horton discloses a vacuum attachment that uses a vacuum pump to create a standing vacuum within a hollow frame/vacuum storage tank. The vacuum storage tank is connected via a hose to a sensing valve in the vacuum cup. Thus, when the sensing valve detects an object, it opens, thereby evacuating the air contained in the vacuum cup into the vacuum. Other examples are U.S. Pat. No. 3,322,454 issued to Mindrum, U.S. Pat. No. 4,561,687 issued to Bostrom, and U.S. Pat. No. 5,431,469 issued to Ohno et al.
Another type of vacuum holding device is disclosed in U.S. Pat. No. 3,845,950 issued to Kuzniak ("Kuzniak") in which a suction box is provided. The suction box of this device is constantly in a partially evacuated condition when in use. Adjacent compartments, which are separated from the suction box by a series of flaps, are normally open to the atmosphere. When the adjacent compartment become blocked by an object, the flaps open to the suction box thereby evacuating the adjacent compartments and securing the object to be held. U.S. Pat. No. 5,035,568 issued to Joulin discloses a similar device.
These devices, however, require a standing vacuum that is accessible upon the detection of an object. This is both wasteful of energy and creates extra maintenance work on the vacuum components.
Therefore, there is a current and continuing need for a vacuum valve that does not require a standing vacuum for operation. There is especially a need for a vacuum valve that creates the needed vacuum only upon the detection of an object, vacuum-on-demand.